According to Mr. Adam Burke, the deadline for completing the four stays is 90 days after sign-up:
Sorry for the confusion on this point! The February 28 deadline is for
registration only -- not for completion of the four stays. The 90 day period to
complete the four stays begins on the day that you register for the promotion.
I've asked the Service Center to issue a note to all reps to make sure we're
providing members with a consistent answer!
Best regards,
Adam